1. Field of the Invention
The present invention relates to a magnetic tape cartridge and, in particular, to a structure for restricting the rotation of a reel when it is not in use after the reel is stored in a cartridge case with a magnetic tape wound thereon.
2. Description of the Related Art
Conventionally, a magnetic tape cartridge, which is used for a video tape or for a magnetic tape for use in an external recording apparatus for a computer, comprises a reel stored in a cartridge case for winding a magnetic tape thereon; and also, the magnetic tape cartridge further includes a rotation restricting mechanism which is used to restrict the rotation of the reel when it is not in use in order to prevent the wrong loading and damage of the magnetic tape due to loosening of the magnetic tape (for example, Page 3 and FIG. 1 of JP-B-3-20833).
And, when the magnetic tape cartridge is mounted into a recording and reproducing apparatus, in case where a rotation restriction removing pin provided on the recording and reproducing apparatus side is inserted into an insertion hole formed so as to communicate with the interior and exterior of the cartridge case, the rotation restriction of the reel by the rotation restricting mechanism can be removed by the rotation restriction removing pin.
Also, in the magnetic tape cartridge of this type, there is formed a positioning hole: that is, when mounting the magnetic tape cartridge into the recording and reproducing apparatus, the positioning pin disposed on the recording and reproducing apparatus side is inserted into the positioning hole to thereby position the magnetic tape cartridge at a predetermined position of the recording and reproducing apparatus (for example, Page 3, FIGS. 2 and 3 of JP-A-5-81747).
However, in the above-cited magnetic tape cartridges, the recording and reproducing apparatus, into which the magnetic tape cartridge is to be mounted, must include not only a pin for removing the rotation restricting mechanism for restricting the rotation of the reel but also a positioning pin for positioning the magnetic tape cartridge at a proper position, which complicates the structure of the magnetic tape cartridge as well as the structure of the recording and reproducing apparatus for mounting the magnetic tape cartridge thereinto. Also, since the interior and exterior of the cartridge case are made to communicate with each other through the insertion hole into which the rotation restriction removing pin is inserted, dust is easy to invade the cartridge case through the insertion hole, which results in the poor dustproof performance of the magnetic tape cartridge.